Traditionally, vanadium is extracted and recovered from its ores through a pyrometallurgical process that involves a salt roasting step followed by water leaching. Environmental concerns are becoming of increasing importance to those wishing to establish new mineral processing operations and those processes that require roasting more often than not emit products that have an overwhelmingly negative environmental impact.
Hydrometallurgical options for the extraction and recovery of vanadium from its ores have not been explored to date, as a rule, as a result of difficulties in both the leach step and the recovery step. With regard to leach and recovery, iron is typically co-extracted with the vanadium, and titanium is often also present, such as may be found in titanomagnetite type ores.
This results in concerns regarding selectivity of any leach and recovery processes. Iron is co-extracted with vanadium in the acid leaching since vanadium is locked as solid solution within the titanomagnetite matrix. Minimising the dissolution of iron in acid leaching is often a challenge without sacrificing the extraction efficiency of vanadium.
Solvent extraction requires that the solution pH be adjusted prior, to the solvent extraction step. This often results in the co-precipitation of iron and vanadium.
Remya et al (Remya et al., Solvent Extraction and Ion Exchange, Vol. 21., No. 4. pp. 573-589, 2003) conducted a study for solvent extraction of vanadium using Cyanex 923. However, there is no disclosure of a full process from leaching to purification step by solvent extraction and stripping and the recovery of vanadium by precipitation. Furthermore, multiple stripping agents are required which may involve extra processing cost in a full scale operation.
Additionally, any potential for economic viability of a hydrometallurgical route for the extraction and recovery of vanadium, and any associated valuable metals, has not been demonstrated.
The method of the present invention has as one object thereof to overcome substantially the abovementioned problems of the prior art, or to at least provide a useful alternative thereto.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. This discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.